Ultrasonic probe and aligned needle guide system

ABSTRACT

A side-fire ultrasonic probe includes an alignment feature that, when used to connect the probe with a needle guide for intra-cavity medical procedures, enables alignment of a needle in an imaging plane of an ultrasonic transducer. The alignment feature is configured such that alignment of the needle within the imaging plane is accomplished when a protective sheath is disposed between the alignment feature and the needle guide. This configuration can be used with high frequency ultrasonic arrays having frequency distributions centered at about 20 MHz, and for medical procedures, such as biopsying organs or other bodily intra-cavity structures, and delivering intra-cavity therapies.

BACKGROUND

The present disclosure relates generally to medical imaging anddiagnostics, and more specifically to an ultrasonic probe and an alignedneedle guide system.

Accessing organs and structures of the human body through body cavitiesis a standard medical technique. In some procedures, diagnostic toolsare inserted into a body cavity to examine or biopsy an organ or otherbody structure. The information collected is then used for the detectionand evaluation of a wide variety of medical conditions. In particular,ultrasonic devices are used to identify intra-cavity structures, such aprostate, by transmitting and receiving ultrasonic waves. The receivedwaves are transformed into an image of the intra-cavity structure, whichcan then be used to navigate a biopsy needle to a desired locationwithin the image.

Ultrasonic transducers used in these medical applications are typicallyencased within an anatomically compatible housing to improve patientcomfort during insertion into the patient. Ultrasonic transducerhousings fall into one of two broad configuration types: “end-fire” and“side-fire.” The end-fire type transmits ultrasonic waves from a tip ofthe housing, whereas the side-fire type transmits from a side-wall ofthe housing. Regardless of the housing type, the ultrasonic image can beused to navigate a biopsy needle to an exterior surface of anintra-cavity bodily structure.

SUMMARY

In one embodiment, an ultrasonic probe of the present disclosureincludes a cylindrical housing that includes a needle guide alignmentfeature on the surface of the housing. The alignment feature is used toconnect a needle guide to the cylindrical housing and to align theneedle guide such that a needle translated through the guide istranslated in an imaging plane of the ultrasonic transducer. Thealignment feature is configured such that the needle is aligned in theimaging plane even when a protective sheath is disposed between thehousing and the needle guide. The protective sheath may facilitatesanitation, sterilization, and re-use of the probe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of an ultrasonic probe with an alignedneedle guide, in an embodiment.

FIG. 2 is a perspective view of a tip of an ultrasonic probe, whereinthe probe is encased in a protective sheath and, using a needle guide, aneedle is aligned in an imaging plane produced by an ultrasonictransducer, the alignment facilitated by an alignment feature disposedon the housing, in an embodiment.

FIG. 3 is perspective view of an ultrasonic probe covered by aprotective sheath and an attached needle guide aligned with the probe,in an embodiment.

The figures depict various embodiments of the present invention forpurposes of illustration only. One skilled in the art will readilyrecognize from the following discussion that alternative embodiments ofthe structures and methods illustrated herein may be employed withoutdeparting from the principles of the invention described herein.

DETAILED DESCRIPTION Overview

Embodiments described herein include a side-fire ultrasonic probe withan alignment feature that, when used to connect the probe to a needleguide for intra-cavity medical procedures (e.g., biopsying organs orother bodily intra-cavity structures, delivering intra-cavitytherapies), facilitates alignment of one or more needles translatedthrough the needle guide with an imaging plane of an ultrasonictransducer. The alignment feature is configured such that alignment of aneedle within the imaging plane is accomplished even when a protectivesheath is disposed between the alignment feature and the needle guide.

By positioning the translated needles within the imaging plane of aside-fire type ultrasonic probe, an ultrasonic image can be used toimage an advancing needle with respect to an intra-cavity structure ofinterest. This ability is particularly useful when the ultrasonictransducer has a frequency and/or resolution sufficient to imageintra-structure or intra-organ features. Simultaneously imaging thestructure of interest and the needle permits navigation of the needle toa specific intra-cavity structure within a human body, or, givensufficient resolution of the ultrasonic transducer, navigation of theneedle to a specific location within the structure. This can thenimprove the diagnostic capability of the procedure or effectiveness ofthe therapy. Allowing for positioning of a needle oriented at differentangles with respect to the probe enables access to a range of locationswithin the body or structure by the needles while reducing themanipulation of the probe. This can improve patient comfort during theprocedure, as well as patient safety.

Ultrasonic Probe and Aligned Needle Assembly

FIG. 1 illustrates an embodiment of a side-fire ultrasonic probeassembly 100 having an alignment feature that enables alignment of aneedle guide 110 such that needles (e.g., any of needles 114A-C, “114”for brevity) translated through the guide are translated into an imagingplane produced by the ultrasonic transducer array. The imaging plane isdefined by a pathway of ultrasonic waves produced by the ultrasonictransducer. The ultrasonic probe assembly 100 includes a cylindricalhousing 104 having a longitudinal axis 108, and a transducer housing 116having an angled face 120. The transducer housing 116 encloses anultrasonic transducer array used for the production of ultrasonic waves,the reflections of which are transformed into images. A protectivesheath 124, disposed between the cylindrical housing 104 and the needleguide 110, covers a portion of the cylindrical housing and thetransducer housing 116. The ultrasonic probe assembly 100 also includesa needle assembly alignment feature 128, shown in more detail in FIGS. 2and 3.

The cylindrical housing 104 of the ultrasonic probe assembly 100 has anumber of uses including, but not limited to, enclosing wiring and/orelectronic components used to operate the ultrasonic transducer,providing a structure with which to connect other elements of theassembly (e.g., the needle guide 110), and providing a proximal end(i.e., a handle) used by an operator for manipulating the assembly. Inthis example, the cylindrical housing 104 has a circular or ellipticalcross-section that is ergonomically insertable into a body cavity, suchas a rectum, to image, biopsy, and/or deliver a therapy to a bodystructure of interest, such as a prostate. While other embodiments ofthe cylindrical housing 104 are not limited to cylinders or circular orelliptical cross-sections, housings having points or edges may causepatient discomfort or damage sensitive tissue. The longitudinal axis 108of the cylindrical housing 104 is parallel to the long axis of thecylindrical housing and is used as a convenient reference whendescribing other features of the embodiments.

The needle guide 110, which includes individual guide channels 112A-C(“112” collectively), into which one or more of the needles 114 can beinserted, is attached to the cylindrical housing 104 over the protectivesheath 124 using the alignment feature 128. The details of the needleguide 110 are described in more detail in the context of FIGS. 2 and 3.

One needle of the needles 114 is used to biopsy intra-cavity structuresof interest, such as a prostate (shown in FIG. 1 by an ellipse), bybeing translated through one channel 112 of the needle guide 110,through port 113 (shown in FIGS. 2 and 3), and into the ultrasonicimaging plane. The three channels 112 are oriented at different angleswith respect to the horizontal axis 108 of the probe assembly 100 sothat different locations within the body structure can be accessed by aneedle 114 without moving the probe within the patient. Because both theneedle (e.g., needle 114A) and the structure of interest are in theimaging plane simultaneously, and therefore both imaged using reflectedultrasonic waves, the needle can be navigated to a specific location ofinterest. This location can be on the surface of the body structure or,provided that the ultrasonic transducer is capable of intra-structureresolution (typically achieved at high transducer frequencies ofapproximately 20 MHz), even within a specific body structure.

The transducer housing 116 is located at the distal end of thecylindrical housing 104. The transducer housing 116 substantiallysurrounds the ultrasonic transducer used to produce ultrasonic waves. Inthis example, the transducer housing 116 is ergonomically shaped toimprove patient comfort during insertion of the assembly 100 into a bodycavity. This ergonomic shape can also improve patient comfort duringoperation of the assembly 100 for imaging and biopsying intra-cavitybody structures.

In this example, because the ultrasonic transducer transmits ultrasonicwaves through a sidewall of the cylindrical housing 104, the design ofthe assembly 100 is sometimes referred to as a “side-fire” design. Otherembodiments of the invention may be used with “end-fire” designs, inwhich the ultrasonic waves are transmitted from a terminal end of thetransducer housing 116 (i.e., in a direction generally parallel to thelongitudinal axis 108).

The transducer housed by the transducer housing 116 may comprise anarray of piezoelectric elements that produce ultrasonic waves whenelectrically actuated. In some examples, the transducer array canproduce ultrasonic waves having a frequency distribution centeredbetween approximately 1 MHz and 12 MHz. The resolution of imagesproduced at these lower frequencies may be sufficient to discern theoutline and/or outer surfaces of intra-cavity body structures. In otherexamples, the transducer array can produce ultrasonic waves having afrequency distribution centered at approximately 20 MHz and a 6 dBcorner frequency of approximately 27 MHz. The resolution of imagesproduced at these higher frequencies may be sufficient to imagestructures within the intra-cavity body structures (i.e., intra-organresolution). This higher resolution and imaging facilitates navigationof the needles 114A-C to locations within the body structure, which canthen be biopsied. Also, because the interior of the organ or bodystructure can be imaged, this resolution can also help preventaccidental damage to the body structure.

The above description of the approximate center of the frequencydistribution is important due to inconsistent description of transduceroperating frequency in the art: while some artisans describe operatingfrequency by citing the center of the frequency distribution, otherartisans describe operating frequency by citing the upper limit of thedistribution.

The side-fire design of the transducer housing 116 includes the angledface 120, which facilitates acoustic coupling between the transducer andthe body structure to be imaged. By matching the angle of the angledface 120 to the shape of the body structure, the transducer and thus theultrasonic waves used to image the body structure are brought proximateto a surface of the body structure without angling the assembly 100 as awhole. This improves the quality of the image and comfort of the patientby reducing the manipulation of the probe 100 needed to acquire animage. In some embodiments, the angled face 120 is angled about 13° tomatch a typical slope of a prostate surface. In other embodiments, theangled face 120 is angled at least 5°. In further embodiments, thisangle can be varied depending on the natural angle (or range of naturalangles) of the body structure surface to be imaged. In still furtherembodiments, the transducer housing 116 does not have an angled face,but rather is a standard side-fire design.

In the example shown, the protective sheath 124 covers the transducerhousing 116, and at least a portion of the cylindrical portion 104.Acting as a barrier, the protective sheath 124 prevents body fluids orother substances from contaminating the assembly 100. By limiting accessof body fluids and contaminants to the interior and exterior of theassembly 100, the protective sheath 124 facilitates sanitation,sterilization, and re-use of the assembly.

In some examples, the protective sheath 124 is designed to match theshape of the assembly 100, including the cylindrical housing 104, thetransducer housing 116, the angled face 120, and the alignment feature128. In other examples, the protective sheath 124 is designed to matchthe shape of conventional ultrasonic probe assemblies and not iscustomized to match the shape of the assembly 100. In some examples, theprotective sheath 124 is made from a polymer, although other materialsthat permit the transmission and reception of ultrasonic waves can beused.

Needle Alignment

The alignment feature 128 is configured such that a 114 is aligned withand disposed in the imaging plane (shown in FIG. 2) when the needleguide 110 is engaged with the alignment feature through the protectivesheath 124 and the needle has been translated through one of thechannels 112 of the needle guide and through the port 113 into theimaging plane. In some embodiments, the alignment feature 128 is anegative feature imprinted, molded, or embossed into the surface ofcylindrical housing 104 and configured to mate with an approximatelymatching positive feature on the needle guide 110. This negative profileenables the needle guide 110 to connect to the cylindrical housing 104,enabling the imaging of a needle 114 during a procedure, as describedabove, while also maintaining an anatomically compatible profile. Inother embodiments, the alignment feature 128 is a positive featureattached, connected, or integrated onto the surface the cylindricalhousing 104. In still other embodiments, the alignment feature 128 is acombination of positive and negative features.

In some examples, the alignment feature 128 is designed to connect theneedle guide 110 to the cylindrical housing 104 and maintain alignmentof the needles 114 in the ultrasonic imaging plane when the protectivesheath 124 is disposed between the cylindrical housing and the needleassembly. In some embodiments of this example, the alignment feature 128can be adjusted to accommodate thickness variations of the protectivesheath 124, thereby maintaining alignment of the needle 114 in theimaging plane regardless of sheath thickness. In other examples, thealignment feature 128 is designed to maintain alignment between theneedle 114 and the imaging plane without adjustment and regardless ofthe thickness of the protective sheath 124.

FIG. 2 illustrates the alignment of the needle 114A in the acousticimaging plane of the ultrasonic probe assembly 100, as discussed above.This figure depicts a portion of the needle guide 110, the alignmentfeature 128, the needle 114A, and an acoustic imaging plane 208. As willbe appreciated, the needle 114A is selected only for convenience.Embodiments of the present disclosure are applicable to the needles 114Band 114C, which can be translated through the corresponding needle guidechannels 112 and emerge from port 113 at different angles with respectto the horizontal axis 108 of the probe 100 into the imaging plane 208.Also shown in FIG. 2 are portions of the cylindrical housing 104, thetransducer housing 116, the angled face 120, and the protective sheath124.

In the example shown, the cylindrical housing 104 and the transducerhousing 116 are protected by the protective sheath 124. The needle guide110 is disposed in the alignment feature 128, in this example a negativefeature on the surface of the cylindrical housing 104, therebycompressing the protective sheath 124 into the alignment feature.

As shown, the needle guide 110, the needle 114A, the alignment feature128, the protective sheath 124, and the transducer are configured suchthat the needle is disposed within the imaging plane 208 when extendeddistally through the needle guide 110. As mentioned above, this enablesthe needle 114A to be viewed during use and, in particular, enables theneedle to be navigated to the body structure of interest. Furthermore,for examples of the ultrasonic probe assembly 100 using a transducerhaving frequencies centered at approximately 20 MHz, the needle 114A canbe navigated to intra-organ features, thereby enabling precision biopsyor treatment of specific intra-organ areas.

In one aspect, this alignment of the needle 114A and the image plane 208is accomplished by configuring the needle guide 110, a needle 114, andthe alignment feature 128 such that the needle is positioned in theimaging plane 208 at a location in the imaging plane that is a functionof how far the needle is translated. This alignment is furtheraccomplished by controlling the dimensional tolerances of the variouscomponents to a total of approximately half of the width of the imagingplane 208. Controlling the total dimensional variation to only a portionof the width of the imaging plane permits some dimensional and/oralignment variation in the various components while still enabling theneedle 114A to be translated into the imaging plane 208.

In one embodiment of the above example, ultrasonic transducers having afrequency distribution centered at about 20 MHz produce an imaging planefrom approximately 300 microns to approximately 500 microns wide. Byconfiguring the various components (e.g., the housing 104, the alignmentfeature 128, the needle guide 110, and the protective sheath 124)described above, and controlling the combined dimensional variation ofthese components to approximately 250 microns, the needle 114A can bereliably imaged during and after its translation into the imaging plane208.

In examples in which the diameter of the needle 114A is larger than theimaging plane 208 (e.g., a needle approximately 1000 microns in diameterused with an imaging plane approximately 500 microns wide), the entirediameter of the needle need not be in the imaging plane to image theneedle and navigate it to a body structure location. Rather, a sectionthat includes the needle point can be used to navigate the needle safelyto, and into, the structure.

Needle Guide

FIG. 3 illustrates an ultrasonic probe 300 that includes an ultrasonictransducer 302, and the needle guide 110 attached to the cylindricalhousing 104 over the protective sheath 124 using the alignment feature128. In this example, the needle guide 110 includes the channels 112A-C,the port 113, a frame 304, a needle housing 308, and a positioningfeature 312.

In this example, the three needles 114A-C are shown in each of the threechannels 112A-C of the needle guide 110 to illustrate the differentangles at which the channels are oriented with respect to thelongitudinal axis 108 of the housing 104. This diversity of angles isused to increase the range of locations within the body accessible bythe needles while minimizing the manipulation required of the assembly100 needed to access these locations. Because the needles 114 in thechannels 112 of the needle guide 110 are positioned at different angles(and can exit port 113 at different angles), they each can be insertedinto a different location in the body without articulating, twisting,translating, or otherwise moving the assembly 100 (as illustrated inFIG. 1). Furthermore, the multiple channels 112 of the needle guide 110(not limited to only the three shown) permit multiple biopsy needles totake samples from different locations within a body structure withoutadditional movement of the assembly 100. This arrangement improvespatient comfort during a procedure requiring the collection of biopsysamples, or the delivery of a therapy, to multiple locations within thebody.

The angles of the channels in the needle guide 110 (and thereforeneedles 114) are determined, in part, by the locations within the bodyor body structure intended to be biopsied, and the depth of penetrationinto a body cavity by the assembly 100 that is needed to access the bodystructure of interest. Other factors used to determine these angles mayinclude the ability to access a wide range of locations within the bodycavity, and the need to maintain the position and/or alignment of theneedles within the imaging plane of the transducer (as shown in FIG. 2).In some embodiments, the channels of the needle guide 110 and theneedles 114 can also be angled to limit or prevent access toparticularly delicate or sensitive body structures near the structure ofinterest (e.g., a nerve bundle near the sphincter during a prostatebiopsy). For example, the needles can be arranged at angles from −5°(i.e., 5 o below the horizontal axis), up to about 30°, although anypractical angle can be used.

In one example, because the needle 114C is inserted into the channel 112of the needle guide 110 that has a greater angle with respect to thelongitudinal axis 108 than the portion of the needle guide used withneedle 114A (which is substantially parallel to the longitudinal axis),the locations accessible by these two needles are different. Therefore,different regions of a body structure can be biopsied withoutmanipulation of the assembly 100 as a whole. In one example, an angle ofa needle is selected to prevent a needle from accidental insertion intoa sphincter nerve bundle proximate to the rectum and prostate. Asmentioned above, regardless of the angle of the needles 114, the needleguide 110 and the protective sheath 124 are arranged such that theneedles are translated into the imaging plane of the ultrasonictransducer.

The frame 304 of the needle guide 110 is used to connect one or more ofthe needles 114 to the needle guide and to connect the needle guide tothe cylindrical housing 104. Additionally, the frame 304 can be usedwith the alignment feature 128 to position the needle guide 110 and theneedles 114 with respect to the imaging plane 208, as described above.In this example, the frame 304 is disposed within a negative alignmentfeature to position and align the needle 114A with the imaging plane 208as described above. The needle housing 308, connected to the frame 304and positioned within a second negative feature molded into thecylindrical housing 104 positions and aligns each of the needles 114with the imaging plane 208 as described above.

The positioning feature 312 is connected to the frame 304 and is used tomore firmly position the needle guide 110 in the alignment feature 128by limiting movement of the frame within the alignment feature inadditional directions. This reduces unintentional movement of the needleguide 110, thereby reducing risk of misalignment between the needles114A-C and the imaging plane 208. In addition to reducing this risk ofunintentional movement, the positioning feature 312 can enable moreprecise alignment of the needles 114A-C with the imaging plane 208. Inthis example, the positioning feature 312 is approximately orthogonal toan edge of the frame 304, thereby limiting movement of the frame in adirection parallel to the edge of the frame.

Other designs of positioning features can be used to reduceunintentional shifting of the frame 304, and therefore the needle guide110, or improve alignment of the needles 114A-C with the imaging plane208. In one example, the needle guide 110 is attached, fixed, orotherwise connected to the housing 308 using a clamp. In anotherexample, the needle guide 110 is attached, fixed, or otherwise connectedto the housing 308 using an elastic band that is properly positionedusing a band guide groove in the needle guide and in the housing. Othertypes of clamps may also be used.

Also, while the needle guide 110 includes multiple channels 112 and canaccommodate more than one needle 114 at a time, other examples include asingle channel 112 and/or a single needle 114.

SUMMARY

The foregoing description of the embodiments of the invention has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the inventive subject matter.It is therefore intended that the scope of the invention be limited notby this detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsof the invention is intended to be illustrative, but not limiting, ofthe scope of the invention, which is set forth in the following claims.

What is claimed is:
 1. An ultrasonic probe assembly comprising: a probehousing having a proximal end, a distal end, a longitudinal axis; anultrasonic transducer array disposed within the distal end of the probehousing, the transducer array configured to produce a plurality ofultrasonic waves that form an ultrasonic imaging plane; a protectivesheath configured to enclose at least the distal end of the probehousing and prevent contamination of the housing; a needle guidealignment feature disposed on a surface of the probe housing; and aneedle guide connected to the probe housing over the protective sheathusing the needle guide alignment feature, the needle guide configured toguide at least one needle into the ultrasonic imaging plane.
 2. Theultrasonic probe assembly of claim 1, wherein the distal end of probehousing comprises a face angled with respect to the longitudinal axis byat least 5° for acoustic coupling between the ultrasonic transducerarray and a body structure.
 3. The ultrasonic probe of claim 2, whereinthe face is angled about 13° with respect to the longitudinal axis foracoustic coupling between the ultrasonic transducer array and aprostate.
 4. The ultrasonic probe assembly of claim 1, wherein theneedle guide comprises at least two channels configured to guide needlestranslated through the channels at two different angles with respect tothe longitudinal axis of the probe housing.
 5. The ultrasonic probeassembly of claim 1, wherein a dimensional variation of the alignmentfeature, a dimensional variation of the needle guide, and a dimensionalvariation of the protective sheath total about 250 microns.
 6. Theultrasonic probe assembly of claim 1, wherein the ultrasonic transducerarray is configured to produce ultrasonic waves having a frequencydistribution centered at about 20 MHz.
 7. An ultrasonic probecomprising: a probe housing having a proximal end, a distal end, and alongitudinal axis; an ultrasonic transducer array disposed within thedistal end of the housing, the transducer array configured to produce aplurality of ultrasonic waves that form an ultrasonic imaging plane; anda needle guide alignment feature disposed on a surface of the housing,the needle guide alignment feature configured to secure a needle guideto the housing with a protective sheath therebetween, wherein the needleguide is arranged to guide a needle within the ultrasonic imaging planewhen the needle guide is attached to the housing.
 8. The ultrasonicprobe of claim 7, wherein the needle guide comprises at least twochannels configured to guide needles translated through the channels attwo different angles with respect to the longitudinal axis of the probehousing.
 9. The ultrasonic probe of claim 7, wherein a dimensionalvariation of the alignment feature, a dimensional variation of theneedle guide, and a dimensional variation of the protective sheath totalabout 250 microns.
 10. The ultrasonic probe of claim 7, wherein thedistal end comprises a face angled with respect to the longitudinal axisby at least 5° for acoustic coupling between the ultrasonic transducerarray and a body structure.
 11. The ultrasonic probe of claim 10,wherein the face is angled about 13° with respect to the longitudinalaxis for acoustic coupling between the ultrasonic transducer array and aprostate.
 12. The ultrasonic probe of claim 7, wherein the ultrasonictransducer array is configured to produce ultrasonic waves having afrequency distribution centered at about 20 MHz.
 13. A biopsy assemblycomprising: a probe housing having a proximal end, a distal end, and alongitudinal axis; an ultrasonic transducer array disposed within thedistal end of the probe housing, the transducer array configured toproduce a plurality of ultrasonic waves that form an ultrasonic imagingplane; a needle guide alignment feature disposed on a surface of theprobe housing; and a needle guide configured to couple to the probehousing by the needle guide alignment feature with a protective sheaththerebetween, the needle guide including at least one needle guidearranged to guide a needle into the ultrasonic imaging plane when theneedle guide is coupled to the probe housing.
 14. The biopsy assembly ofclaim 13, wherein wherein the needle guide comprises at least twochannels configured to guide needles translated within the channels attwo different angles with respect to the longitudinal axis of the probehousing.
 15. The biopsy assembly of claim 14, wherein a dimensionalvariation of the alignment feature, a dimensional variation of theneedle guide, and a dimensional variation of the protective sheath totalabout 250 microns.
 16. The biopsy assembly of claim 13, wherein thedistal end comprises a face angled with respect to the longitudinal axisby at least 5°, thereby configured to facilitate acoustic coupling witha body structure.
 17. The biopsy assembly of claim 16, wherein the faceis angled approximately 13° with respect to the longitudinal axis,thereby configured to facilitate acoustic coupling with a prostate. 18.The biopsy assembly of claim 13, further comprising an ultrasonictransducer array disposed within the distal end of the cylindricalhousing and configured to produce a plurality of ultrasonic waves. 19.The biopsy assembly of claim 18, wherein the ultrasonic transducer arrayis configured to produce ultrasonic waves having a frequencydistribution centered at about 20 MHz.
 20. An ultrasonic probe assemblycomprising: an ultrasonic probe configured to image a bodily structurelocated in an imaging plane of the probe, the probe having alongitudinal axis; means for guiding a needle into the imaging plane ofthe ultrasonic probe at one of multiple angles with respect to thelongitudinal axis of the ultrasonic probe; means for physicallypreventing contamination of the ultrasonic probe during use within apatient; and means for coupling the guiding means to the ultrasonicprobe through the contamination prevention means.